Antistatic treating solution for polyacrylonitrile fibers and method



United States PatentfO ANTISTATIC TREATING SGLUTIQN FOR PULY- Y This invention relates to the provision of an antistatic finish, and more particularly to a method for treating polyac rylonitrile fibers to diminish the tendency thereof to accumulate a charge of static electricity.

The problem of preventing the accumulation of surface charges on textiles has plagued the industry for many years and a considerable amountof time and effort has been spent in an attempt to. Obtain a successful solution. There are many compositions suggested in the prior art to be employed asantistatic agents. However, the heretofore employed antistatic agents suffered from many disadvantages including insufficient reduction of static electricity, poor stability over prolonged periods of storage, and the fact that the treated textile had antistatic properties for only a comparatively short period of time so that the antistatic treatment had to be renewed after relatively few launderings or dry cleanings.

The problem is accentuated in the treatment of polyacrylonitrile fibers which not only tend to accumulate a charge-of static electricity, but which also have a tendency to yellow or become otherwise discolored under conditions of elevated temperature often met with in the handling of such fibers as in such textile operations as carding, Weaving, spinning, knitting, and the like. Antistatic treatments heretofore proposed have for the most part actually aggravated or increased this yellowing tendency. It is an object of this invention to provide a method for diminishing the tendency of polyacrylonitrile fibers to accumulate a charge of static electricity which will not be subject to one or more of the above disadvantages. Another object of this invention is the provision of such a method which will not further yellow the fibers being treated and/or whichwill tend to decrease the tendency such fibers have to yellow under conditions of elevated temperatures. Still another object of this invention is the provision of polyacrylonitrile fibers having a reduced tendency .to accumulate a charge of static electricity. Other objects and advantages will appear as the description proceeds. e

The attainment .of the above objects is made possible by the present invention which includes a method, for diminishing the tendency of polyacrylonitrile fibers .to

accumulate a charge of static electricity comprising treating such fibers 7 1 (1) With an aqueous mediumwhich in at least'5% cone. is i g (2) At a pH of from about lj to 4.0 V 1 (3) Containing a'member of the group consisting of (a Freemonoand diacid phosphate esters of a nonionic surface active agent having the molecular configuratioriof a condensation product of at least one moleof an alk'ylene oxide of 2 to 4 carbon atonis with one mole of a compound containing atom, and mixtures thereofiand V (l1) Mixtures of; such free acid phosphate esters with their salts of arnpholytic compounds. It has, been found thatsthe above definedprocess of the present-invention.enables the provision of 'polyacr'ylonit'rile fibers with increased and/or more permanent antistatic properties, reduced tendencies'to yellow, and the like.

In addition, the treatment is advantageous in having a at least 6 carbon atoms and a reactiveghydrogenu reduced tendency to corrode metal equipment employed in the treatment of such fibers.

By the term polyacrylonitrile fiber is meant a fiber composed substantially wholly of acrylonitrile homopolymers or composed of heteropolymers, copolymers and/or graft polymers of acrylonitrile and up to 30% by weight of other polymeric materialsuch as vinyl chloride or acetate, styrene, methacrylic acid, chloracrylic acid, and their amides, nitriles, chlorides, esters and the like. Other modifying agents may of course be present in the fiber.

. Such materials, and methods for their manufacture are disclosed for example in U.S. Patents 2,527,863, 2,548,-

282, 2,558,735, 2,595,848, etc. Especially advantageous results are obtained when the present process is applied to fibers containing from to parts by weight of an acrylonitrilepolym'er selected from the group consisting of polyacrylonitrile anda copolyrner containing from 70 to 95% by weight of acrylonitrile and from 30 to 5% by weight of another polymerizable ethenoid monomer se-' lected from the group consisting of a vinyl ester of a saturated fatty acid containing from 2 to 4 carbon atoms,- an isop'ropenyl'ester of a saturated fatty acid containing from 2 to 4 carbon atoms, an acrylic acid alkyl ester, 21

methacrylic acid alkyl ester, vinyl chloride, vinylidene' g the present process are known compounds, being derived from known nonionic surface active agents as made for example by reaction of from 1 or-2 up to or more moles of an alkylene oxide of 2 to 4 carbon atoms with one mole of a compoundcontaining at least 6carbon atoms and a reactive hydrogen atom.

' The alkylene oxide employed in the production of the precursor nonionic surfaceactive agents may be propylene oxide, butyleneoXide, isopropylene oxide, isobutylene oxide, epichlorhydrin, or preferably-ethylene oxide. As compounds to be reacted therewith containing afreactive hydrogen atom there may be mentioned generally saturated or unsaturated, straight or branched, natural or synthetic alcohols such as l'auryl alcohol, oleyl alcohol, Oxo tridecyl alcohol, alcohols of the Pluronic type or their monoether'or monoester derivatives as disclosed for example in U.S.--Patent2,674,619, and the likejphen'ols such as phenol per se and alkyl phenols containing 10 to 61 carbon atoms and including mono-, di-, and tri-butyl;

-nonyl, and -octa clecylphenol, -cresol. and the like, thiols such as dodecyl mercaptamlthiophenol, thionaphthol, benzo-rnercaptan and the like, primary and secondary amines such as lauryl. amine, stearyl amine, dioctyl amine,

'and the like and the carboxylic and sulfonic acids and their: amides such as lauric, oleic, and stearic acid and their arn1des,'dodecyl and dodecyl benzene sulfonic acids and sulfonamides, and-.the like. The-foregoing reactive: hydrogen-containing compounds. are merely illustrative,

a more complete disclosure of such compounds, their condensation products with alkylene oxides suitable for phosphation to. produce the phosphateestersoperative herein appearingflfor exarnple in U.S. Patent 3,004,056

and 3,004,057; Accordingly,: such disclosures in said patents, so far as they relateto' the production of'free s monoanddiacid phosphate esters of nonionic surface active agents having. the molecular configuration of condensation product of at least one mole of analkylene oxide of 2 to 4 carbon atoms with one rnole of a compoundcontainingat least 6 carbon atoms and a reactive corporated herein byreference thereto. 7 Such patent dis.-

Patented Fells. 23, 1965 3,004,056 and column 2, line 14 to column 5, line '37 and column 5, line 57 to column 6, line 37 of US. Patent 3,004,057.

While any method may be employed for phosphating the above defined nonionic surface active agents, as for example by reaction of such agent with polyphosphoric acid, phosphorous oxychloride, and the like, unexpectedly improved results are obtained when phosphate esters are employed herein as produced by the processes disclosed in said US. Patents 3,004,056 and 3,004,057. The process of US. 3,004,056 broadly comprises reacting one mole of P with 2 to 4.5 moles of the nonionic surface active agent under substantially anhydrous conditions and at a temperature below about 110 C. down to about room temperature. The process of US. Patent 3,004,057 is an improvement involving carrying out the aforementioned reaction in the presence of a small amount of a phosphorus-containing compound such as hypophosphorous acid, salts of hypophosphorous, phosphorous acid and salts and esters of phosphorous acid, preferably hypophosphorous acid or sodium hypophosphite.

'As pointed out in the aforementioned patents, the products there produced are complex in nature, generally containing about 20 to 45% of the secondary (mono-acid) phosphate ester, 30 to 80% of the primary (di-acid) phosphate ester, and 0 to 40% of the unreacted nonionic surface active agent. products may also be present. A similar phosphating process may be employed in which relatively higher proportions of P 0 are reacted with the nonionic agent, as for example from about 0.5 to 3 moles of P 0 per mole of nonionic. Such a process would likewise yield mixtures of monoand di-acid phosphate esters, though perhaps in different proportions with little or no tertiary phosphate esters.

The use of the above described free monoor ,diacid phosphate esters, or preferably mixtures thereof, for the treatment of polyacrylonitrile fibers has been found to be not only highly effective for imparting improved antistatic and lubricant properties to such fibers, but in addition yields fibers which for the most part are no yellower than untreated fibers when subjected to the same conditions of elevated temperatures. This treatment is in fact unexpectedly eifective when applied to the fibers described and claimed in US. Patent 2,790,783 in that the treated fibers are decolorized or yellowed less than the corresponding untreated fibers under conditions of elevated temperatures. These acid phosphate esters are applied to the'fiber from an aqueous medium having a pH of about 1.5 to 3.5 and concentrations ranging from about 0.1 to

. by weight to deposit about 0.05 to 3% of the phosphate esters O.W.F. (on the weight of the fiber).

As a further feature of the invention, it has been found that further improved antistatic and lubricating properties are obtained when a very small proportion of the above.

described free acid phosphate esters are neutralized in the aqueous medium with a salt of an ampholytic compound. Since it has been found that increased neutralization is increasingly detrimental to the desired anti-yellowing properties, it is important to limit the use of such ampholytic compounds for neutralization purposes so as to prevent the pH of the medium from exceeding a value of 4 when in the form of a medium having a concentration of at least 5% of the phosphate esters. The maximum permissible proportion of ampholytic compound to be employed for neutralization, through readily ascertainable by routine experimentation in any particular instance, will vary with the type of acid phosphate ester being neutralized, the type of ampholytic compound employed, the type and concentration of the aqueous medium, and the like, and can therefore not be accurately defined in gen eral terms of proportions or concentrations. Even minute,

Small amounts of unidentified by- The above referred to ampholytic compounds are well known, being generally organic compounds containing at least one basic amino group and at least one acid group such as carboxylic, sulfonic, phosphoric, phosphonic, or the like whereby the compound can act simultaneously as an acid or a base. By way of illustration only, there may be mentioned as suitable ampholytic compounds amino carboxylic acids such as ethylenediamine tetraacetic acid, N-hydroxyethyl ethylenediamine triacetic acid, N-triacetic acid, a-aminobutyric acid, gamma-aminobutyric acid, ca-aminopentanoic acid, and glycine, and the like, and amino sulfonic acids such as taurine, gamma-aminopropane-sulfonic acid, other or, B, gamma, and omega alkane sulfonic acids and the like, and the N-alkyl (methyl, nonyl, octadecyl, etc.), aralkyl (benzyl), and cycloalkyl (cyclohexyl) substituted derivatives of such aminocarboxylic, aminosulfonic, aminophosphoric, and aminophosphonic acids and the like. For neutralization of the above described acid phosphate esters, these ampholytic compounds are employed in the form of their salts (of the acid radicals therein) with cations such as alkali metals including sodium, potassium and lithium, alkaline earth metals including calcium, strontium, and magnesium, ammonium, and aliphatic, alicyclic, aromatic and heterocyclic organic amines such as mono-, diand tri-methylamine, -ethylamine, -propylamine, -laurylamine, -stearylamine, -ethanolamine, -butanolamine, -hexanolamine, -cyclohexylamine, -phenylamine, -benzylamine, pyridine, morpholine, and the like. In the usual case, up to about 10% of the ampholytic compound by weight of the acid phosphate esters present in the aqueous medium may be employed with neutralization without exceeding the maximum permissible pH of 4 (in at least 5% concentration) The polyacrylonitrile fibers treated in accordance with this invention may be in any of the usual forms and in natural bulk, interwoven or felted form as for example in the form of staple fiber or continuous filaments in bulk form or in the form of tow, rope, yarns, slubbings, warps, fabrics, felts, and the like, and treated as a wound package, running length, fibrous stock, bulk, etc. Further, although this invention has been described for use in the treatment of fibers it will be understood that the process may be employed for the similar treatment of other polyacrylonitrile articles including film and sheet material and other objects of any size, shape and configuration without departing from the spirit and scope of this invention.

The term aqueous medium is intended to include solutions, dispersions or stable colloidal suspensions, which medium containing the above described acid phosphate esters or mixtures of such esters with their salts with ampholytic compounds may be applied to the fiber by immersion, padding, spraying, or in any other desired manner. It will also be understood that the water in the aqueous medium may be replaced in part by a water miscible, polar organic solvent such as acetone, alcohol, dioxane, dimethyl-formamide, or the like.

Further, the above described aqueous medium employed in the process of this invention may contain other adjuvants commonly employed for the treatment-of fibrous material to facilitate their manufacture, including for example detergents and washing agents such as sulfonated fatty alcohols, sulfonated oils and other sulfonated compounds, and nonionic surface active agents of the type described above as precursors for the phosphate esters employed herein, lubricants such as sperm oil, castor oil,

light sinker oil, combing oil,'in addition to thickening agents, glycerine, urea, soaps, and the like.

The following examples are only illustrative of preferred embodiments herein, and are not to be regarded as limitative. All parts and proportions referred to herein and in the appended claims are by weight unless otherwise indicated.

EXAMPLE 1 The phosphate ester mixture disclosed in Example 3 of action of one mole of P with four moles of the condensation product of one molecular equivalent of nonylphenol with six molecular equivalents of ethylene oxide, is dissolved in water in varying amounts to' give solutions having the concentrations and pH values listed in Table I below. Samples of wet polyacrylonitrile fiber tow produced by the process of Examples 2 or 7 of US. Patent, 2,790,783 are soaked in these solutions overnight, centrifuged to remove excess solution, dried and heat treated, together withan untreated control sample, in a velocity oven at 150? C;for 30 minutes.

An examination of the resulting heat treated samples shows thatthe control sample is slightlyyellow whereas the samples treated with solutions of said phosphate ester mixture are pure white like the original fiber.

The antistatic properties of the heat treated samples of tow are evaluated at 50% relative humidity in accordance with the AATCC Standard Test Method 76-4959- Determination of the Electrical Resistivities of Fabric. The results of this evalution are listed in the right hand column of Table I below showing that the phosphate ester-treated samples have substantially better (lower resistivity) antistatic properties than the untreated control, it being important to note that the maximum resistivity measured by the sensitive equipment is 14.00 and that a difference of 0.5 in the measured resistivity is significant.

' EXAMPLE 2 To 190.0 g. of tap Water is added 10.0 g. of the phosphate ester mixture employed in Example 1 above and the sample shaken until no solution is visible. This 5% solution has a pH of 2.0 To this solution is added a minute amount of a 50% aqueous solution of sodium N-methyl tauride whereby the pH of the solution is increased to 2.5 but with no significant Weight increase. A portion of this solution is diluted with tap water to give a 1.0% application bath having a pH of 2.75.

When the resulting application bath is applied to polyacrylonitrile fiber and the treated fiber heat treated as described in Example 1, the resulting fiber is found to be no yellower than the control.

EXAMPLE 3 To a 5% acid phosphate ester solution prepared as described in Example 2 is added 1.4 g. of a 50% aqueous EXAMPLE 4 To a 5% acidphosphate ester solution prepared as described in Example 2 is added 5.2 g. of a 16% aqueous 1', has a resistivity of 10.78 log a. solution of sodium sarcosinate, yielding aso'lution having a pH of 3.5. A portion of this solution is diluted with tap water to give a 0.25% application bath having a pH of 5.7.

When the resulting application bath is applied to p'olyacrylonitrile fiber and the treatedfiber heat treated as described in Example l, the resulting fiber is found to be no yellower than the control.

-The heat treated fiber tested for antistatic properties as described in Example 1, has a'resistivity of 11.18 log ohms/ sq.

This invention has been disclosed with respect to certain preferred embodiments thereof, and it is to be understood that modifications and variations thereof obvious,

to persons skilled in the art are to be included within the spirit and purview of this application and the scope of the appended claims. We claim: 7

1. A method for diminishing the tendency to accumulate a charge of static electricity of polyacrylonitrile fibers comprising by weight from 70 to parts of an acrylonitrile polymer selected from the group consisting of 'polyacrylonitrile and a copolymer containing from 70 to 95% of acrylonitrile and from 30 to 5% of another pclymerizable ethenoid monomer selected from the group consisting of a vinyl ester of a saturated fatty acid conwhich is a condensation product of at least one mole of analkylene oxide of 2 to 4 carbon atoms with one mole of an alkyl phenol containing 10 to 61 carbon atoms, and (b) salts of said phosphate esters with organic ampholytic compounds containing at least one basic amino group and at least one member of the group consisting of carboxylic, sulfonic, phosphoric and phosphonic acid groups, said salts being present in an amount insufficient to raise the pl-I'of said solution above 4.0 when the concentration of said mixture of (a) and (b) in said solution is at least 5% by weight, and then drying the treatedrfibers to deposit thereon about 0.05 to 3% of said mixture of (a) and (b) by weight of the fibers. a 2. A method as defined in claim 1 wherein said alkylene oxide is ethylene oxide and said alkyl phenol is nonyl phenol. 1

3. A method as defined in claim 1 wherein component (b) constitutes salts of said phosphate esters with sodium sarcosinate.

4. A method as defined in claim 1 whereincomponent (b) constitutes salts of said phosphate esters with sodium N-methyl tauride.

5. Polyacrylonitrile fibers as defined in claim I carrying about 0.05 to 3% by weight of said fibers of a mixture atoms with one mole of an alkyl phenol containing 10 to 61 carbon atoms, and

(b) salts of said phosphate esters with organic 10% by weight aqueous solution of a mixture consisting m 0 d c: ampholytic compounds containing at least one (b) constitutes salts of said phosphate esters with sodium basic amino group and at least one member of N-methyl tauride. the group consisting of carhoxylic, sulfonic, v phosphoric and phosphonic acid groups, References Cited 1n the file of this patent said sa1ttsh beirliig pfresergt inl amgunt zisyificgientfl-to 5 vUNITED STATES PATENTS raise e p 0 sm so u ion a ove W en e concentration of said mixture of (a) and (b) in said 23 5 122 23 a1 solution is at least 5% by Weight. ""f

7. A solution as defined in claim 6 wherein said alkyl- 22 et k g ene oxide is ethylene oxide and said alkyl phenol is nonyl 10 2842462 g 1958 phenol.

8. A solution as defined in claim 6 wherein component gergman 58 (b) constitutes salts of said phosphate esters with sodium Z 3555 a g Sarmmae" 3,056,744 Copes et a1. Oct. 2, 1962 9. A solution as defined in claim 6 wherein component 15 

1. A METHOD FOR DIMINISHING THE TENDENCY TO ACCUMULATE A CHARGE OF STATIC ELECTRICITY OF POLYACRYLONITRILE FIBERS COMPRISING BY WEIGHT FROM 70 TO 95 PARTS OF AN ACRYLONITRILE POLYMER SELECTED FROM THE GROUP CONSISTING OF POLYACRYLONITRILE AND A COPOLYMER CONTAINING FROM 70 TO 95% OF ACRYLONITRILE AND FROM 30 TO 5% OF ANOTHER POLYMERIZABLE ETHENOID MONOMER SELECTED FROM THE GROUP CONSISTING OF A VINYL ESTER OF A SATURATED FATTY ACID CONTAINING FROM 2 TO 4 CARBON ATOMS, AN ISOPROPENYL ESTER OF A SATURATED FATTY ACID CONTAINING FROM 2 TO 4 CARBON ATOMS, AN ACRYLIC ACID ALKYL ESTER, A METHACRYLIC ACID ALKYL ESTER, VINYL CHLORIDE, VINYLIDENE CHLORIDE, STYRENE AND AMETHYLSTYRENE, AND FROM 30 TO 5 PARTS OF POLY-N-VINYL PYRROLIDONE. SAID METHOD COMPRISING TREATING SUCH FIBERS WITH AN ACIDIC, ABOUT 0.1 TO 10% BY WEIGHT AQUEOUS SOLUTION OF A MIXTURE CONSISTING OF (A) A MIXTURE OF FREE MONO- AND DI- ACID PHOSPHATE ESTERS OF A NONIONIC SURFACE ACTIVE AGENT WHICH IS A CONDENSATION PRODUCT OF AT LEAST ONE MOLE OF AN ALKYLENE OXIDE OF 2 TO 4 CARBON ATOMS WITH ONE MOLE OF AN ALKYL PHENOL CONTAINING 10 TO 61 CARBON ATOMS, AND (B) SALTS OF SAID PHOSPHATE ESTERS WITH ORGANIC AMPHOLYTIC COMPOUNDS CONTAINING AT LEAST ONE BASIC AMINO GROUP AND AT LEAST ONE MEMBER OF THE GROUP CONSISTING OF CARBOXYLIC SULFONIC, PHOSPHORIC AND PHOSPHONIC ACID GROUPS. SAID SALTS BEING PRESENT IN AN AMOUNT INSUFFICIENT TO RAISE THE PH OF SAID SOLUTION ABOVE 4.0 WHEN THE CONCENTRATION OF SAID MIXTURE OF (A) AND (B) IN SAID SOLUTION IS AT LEAST 5% BY WEIGHT, AND THEN DRYING THE TREATED FIBERS TO DEPOSIT THEREON ABOUT 0.05 TO 3% OF SAID MIXTURE OF (A) AND (B) BY WEIGHT OF THE FIBERS. 